This invention relates to a device for the assembly of a straight spigot and flange of two pipeline elements, containing an annular axial compression elastomer sealing gasket, this gasket containing a support body for bearing against a pressure counter flange, and in front of this body and interdependent of this body, a support heel for bearing against the flange. An exterior radial surface of the body is designed to rest on the reaction surface of the counter flange; an interior radial surface of the body is designed to rest on the exterior radial surface of the straight spigot; and a forward surface of the heel is designed to press against the flange to insure waterproofness of the assembly of the two pipeline elements.
The words forward and backward are to be understood to refer to the direction of movement of the counter flange during the compression of the gasket.
Such a device is used to assemble pipes, notably ductile cast iron pipes, or for the assembly of a pipe with plumbing such as a shutoff valve. For such an assembly, the counter flange and then the gasket are generally inserted over the straight spigot of a first pipe. Then this is brought close to the flange of another pipe or of a plumbing device. The counter flange is generally linked to the flange by bolts, which, when tightened, bring the flange closer to the counter flange and thus ensure the compression of the gasket. The gasket body then lodges itself in the annular compression chamber delimited by the counter flange reaction surface and the radial exterior surface of the straight spigot.
The sealing gasket must function well in the event that the radial play between the counter flange and the straight spigot and/or the axial play between the flange and the straight spigot are substantial, or in the event that such plays are minimal, in order to be able to adapt to the various configurations generally encountered.
However, these requirements are hardly compatible. Actually, in the first case, the space available for the expansion of the elastomer of the compressed gasket is relatively great. Later on, this gasket must have sufficient size to insure proper function. However, in the second case, the space available for the expansion of the elastomer is relatively small. Then we very frequently notice, especially when radial play is minimal, a poor positioning of the gasket during the compression, notably between the heel and the flange, which leads to weak waterproofness.
For a locked assembly between two pipeline elements, inserts are generally provided in a section of the rear extremity of the body, each insert presenting an interior radial surface into which a catching relief is designed to bear against the exterior radial surface of the straight spigot of the first pipe to lock the two pipes together.
When the play is minimal, notably at minimal radial play, we also notice problems in the positioning of the gasket with, for example, the appearance of rolls of elastomer expansion on the outside of the counter flange, on the rear of the counter flange, and/or with undulation of the elastomer around inserts, which can lead to weak waterproofness between the pipes.